Book/Report

FZJ-2019-03754

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Defektspezifische Kristallzucht von Galliumarsenid mit dem vertikalen Bridgman-Verfahren und Untersuchung von versetzungsnahen Defektzonen

Becker, T.FZJ* ; Sonnenberg, K.FZJ*

1998
Forschungszentrum Jülich, Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/22407

Report No.: Juel-3549

Abstract: GaAs crystals have been grown by the vertical Bridgman technique and have been analysed by various methods, particularly by near infrared microscopy. The main objective of the present work was to study defect zones which form in doped GaAs around dislocations as a result of reactions between impurities and dislocations. A new model for the formation of defect zones is proposed and experimental results are presented which provide strong evidence for the defect model. For this purpose crystals were doped with different impurities and the zone formation was also studied for different stoichiometric conditions. The new defect model assumes that impurities occupying the As sublattice exchange their substitutional position with As interstitials. This process provides fast diffusing interstitial impurities which can be gettered (probably by forming precipitates) at the dislocation. As a result a diluted defect zone is generated around dislocations. The zone becomes visible by NIR phase contrast through the change of the refractive index in the zone. This change in turn is due to the variation of the free carrier concentration which is proportional to the impurity concentration. According to our model we expect only those impurities to contribute to the formation of the defect zone which occupy As lattice sites (e. g. B$_{AS}$, Si$_{AS}$, Ge$_{AS}$, S$_{AS}$, Se$_{AS}$, Te$_{AS}$) but not those on Ga lattice sites (Zn$_{Ga}$, Sn$_{Ga}$, Si$_{Ga}$, Ge$_{Ga}$). This is confirmed by the experimental results. Also confirmed is the expected change in the carrier concentration in the defect zone which depends on the electrical character of the impurities, i. e. $\Delta$n$_{e}$ < 0 for S$_{AS}$, Se$_{AS}$ and Te$_{AS}$ (donors) and $\Delta$n$_{e}$ > 0 for Ge$_{AS}$, B$_{AS}$ and Si$_{AS}$ (acceptors). Since the diffusion mechanism is initiated by As interstitials the formation of defect zones is found to be strongly suppressed if the crystals are grown from a Ga-rich melt (S, Se, Te and Ge-doped GaAs). The dilution of impurities occupying As lattice sites within the defect zone is also confirmed by the study of photoluminescence spectra of Ge and Si-doped GaAs. [...]

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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